Integrated circuit switches used in integrated circuits can be formed from solid state structures (e.g., transistors) or passive wires (MEMS). MEMS switches can be used in a variety of applications, primarily analog and mixed signal applications. One such example is cellular telephone chips containing a power amplifier (PA) and circuitry tuned for each broadcast mode. Integrated switches on the chip would connect the PA to the appropriate circuitry so that one PA per mode is not required.
Depending on the particular application and engineering criteria, MEMS structures can come in many different forms. For example, MEMS can be realized in the form of a cantilever structure. In the cantilever structure, a cantilever an (suspended electrode) is pulled toward a fixed electrode by application of a voltage. The voltage required to pull the suspended electrode to the fixed electrode by electrostatic force is called pull-in voltage, which is dependent on several parameters including the length of the suspended electrode, spacing or gap between the suspended and fixed electrodes, and spring constant of the suspended electrode, which is a function of the materials and their thickness.
MEMS can be manufactured in a number of ways using a number of different tools. In general, though, the methodologies and tools are used to form small structures with dimensions in the micrometer scale with switch dimensions of approximately 5 microns thick, 100 microns wide, and 200 microns long. Also, many of the methodologies, i.e., technologies, employed to manufacture MEMS have been adopted from integrated circuit (IC) technology. For example, almost all MEMS are built on wafers and are realized in thin films of materials patterned by photolithographic processes on the top of the wafer. In particular, the fabrication of MEMS uses three basic building blocks: (i) deposition of thin films of material on a substrate, (ii) applying a patterned mask on top of the films by photolithographic imaging, and (iii) etching the films selectively to the mask.
To fabricate MEMS structures as well as other active or passive devices on a chip, metrology structures are typically implemented in the kerf area. The metrology structures assist in the fabrication of the devices on the chip, by providing alignment marks, as well as used as a means to measure focal planes for performing more accurate lithographic and etching processes, e.g., etching of wiring layers that were deposited at different levels of an insulator layer. The metrology structures are in some cases fabricated from a polymer material which remains encapsulated within insulator material (e.g., oxide) within the kerf structure after formation of the MEMS or other device. However, due to subsequent high temperature processing, the metrology structures are prone to deformation or explosion, resulting in damage to the chip structures and hence reduced yield.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.